OK so I have a canopy over my 90g that has 6.5" of clearance between the water and top of the canopy. Enough for t5 lights, which I'm considering, but also don't want to rule out mh. It is my understanding that 6.5" is definately not enough to house a mh pendant within the canopy (which is entirely open in the back, and I can add fans to add circulation).

My canopy top has a glass top that is partitioned into two folding glass panels. This glass top is currently a tinted glass. I don't have anything over the tank itself, but may put eggcrate on it (not decided).

If I were to swap this glass on the canopy with clear glass, or perhaps just use eggcrate (wouldn't look at nice), can I put a mh pendant suspended above the canopy, so it would be 1/2-1": above the canopy but potentially glass bet the mh light and the tank? Or put a mhdiy pendant right on the glass or perhaps elevated by little metal legs to accomodate air exchange?

This glass top is a PIA, I wish I thought of this before making the purchase. I may wind up doing my own new canopy, or building some extentions to the canopy to raise it up a bit. Just looking at a MH option

So the canopy has frosted glass on the top? And to access the tank you slide the top glass over to one side? If thats the case this is indeed a new canopy design that I havent seen or heard before.

MH will produce alot of heat and I wouldnt put the bulb right over the glass even with little legs. If the top is glass then you cant use a reflector and mount the bulb horizonal either. If you removed the glass and built up the canopy another 6" or so you could mount MH bulbs in the canopy over the tank. With a 90 gal tank you will need two MH bulbs. YOu would then need to develop some other way of accessing the tank. I would be worried that eggcrate to close to the MH would only result in the bulb melting the plastic.

A rcent innovation is the high-intensity fluorescent lamp. These HO or VHO lamps commonly come in 65w and 110w, 48-inch lengths, actinic and full-spectrum wave lengths and requier a remote electonic ballast. They're an alternative to metal halides for deep reef aquariums, but the cost of the electronic ballast is not much different.*
Electronic ballast are nonflickering instant-starting, with little heat output.

So the canopy has frosted glass on the top? And to access the tank you slide the top glass over to one side? If thats the case this is indeed a new canopy design that I havent seen or heard before.

MH will produce alot of heat and I wouldnt put the bulb right over the glass even with little legs. If the top is glass then you cant use a reflector and mount the bulb horizonal either. If you removed the glass and built up the canopy another 6" or so you could mount MH bulbs in the canopy over the tank. With a 90 gal tank you will need two MH bulbs. YOu would then need to develop some other way of accessing the tank. I would be worried that eggcrate to close to the MH would only result in the bulb melting the plastic.

Sorry if I didn't explain this well. It is a Sedona canopy, which has two large openings on the top of the canopy covered by a tinted glass. The glass is split in half, but connected via a rubber split, which allows you to access the top of the tank by just flipping open half the top. I should really submit a picture.